This invention relates to a rolling unit for a bar or the like rolling mill. More particularly, the invention relates to a rolling unit of the type including a supporting casing which contains the mill rollers and their supports, the bearings and seals which isolate an oil circuit from an emulsion circuit.
A rolling unit of this type is placed on a bed, generally in line with other units, and derives its motion from a drive through a clutch, usually of the dog type. The drive is constructed such that each unit will receive its motion at an accurately preset rpm according to the position it occupies along the rolling train.
The unit generally includes three rollers having axes arranged at 120.degree. from one another, two of the rollers being driven rollers and one the main roller. The latter is mounted on a shaft which derives its motion from the drive through a clutch and transmits it to the shafts of the driven or secondary rollers through respective bevel gear pairs.
A rolling unit of this type is described, for example, in UK Patent No. 1,202,792.
The main shaft, which protrudes from the support casing to engage with the drive, is supported on bearings accommodated within bores in the support casing. With such a rolling unit, the rollers are assembled in the following manner.
The main shaft is first arranged with the bevel gear and bearing at the clutch end and then inserted partly through the casing; thereafter, the respective roller is lowered through an opening in the casing with a radial movement relatively to the shaft, the roller is slid over the shaft, and the shaft is pushed into position. Inserted next are the second bearing, second bevel gear, and locking members, which are all passed through the bore located at the remote end from the clutch.
The two secondary rollers, and respective bevel gears, are instead arranged on respective shafts supported on bearings which are provided in bores formed in a secondary support stand (also called "box") which is secured to the casing by means of screws, after it has been inserted in a completely assembled state into a seat specially formed in the casing.
This type of construction results, therefore, in a relatively difficult and time-consuming assembling procedure. It also exhibits some limitations as regards the roller calibration, i.e. fine position adjustment thereof in order that the surface of the rollers which will contact the rolled metal is arranged such as to provide a rolling section concentrated along the theoretical rolling axis and being exactly the same as preset by calculation.
With a rolling unit of the type described above, the main roller is mounted fixedly, namely it can be adjusted neither axially nor radially. The two secondary rollers are instead adjustable, both axially and radially by means of shims interposed between the bearings and box, and between the box and unit. However, the axial adjustment involves a first attempt, measurement, disassembly, replacement of shims, and then final assembling. Adjustment in the radial direction requires a less complicated but just as long disassembly procedure. In other words, a rolling unit of the type just described exhibits some important disadvantages when adjustment is required.
In U.S. Pat. No. 3,987,657, a less complicated arrangement for axially adjusting the secondary rollers has been proposed already, which affords adjustment from outside the rolling unit, without requiring roller disassembly. The rollers are, in fact, mounted on cylindrical mounts which can be shifted axially and have a peripheral thread with which a ring element engages whose rotation, achieved through a gearing means, produces an axial displacement of the respective roller. Radial adjustment is instead achieved by shimming, and accordingly, with relatively complex operations.
That approach, while affording definite advantages as regards roller axial adjustment capabilities, does not fully overcome the assembling difficulties, in particular of the main shaft and roller, and still requires long assembling and servicing times.
It should be considered, in fact, that the cited difficulties are not only encountered upon initial assembling, but also whenever it becomes necessary to replace worn out rollers and/or bearings; an operation this one which may have to be performed already after a few days' interval since the roller life may be limited in some cases to a matter of days.